It is well established that HTLV-I is the etiologic agent for a number of diseases, including adult T-cell leukemia and a neurological disorder called HAM/TSP. In addition, accumulating evidence suggests that HTLV-II may be involved in disease, as well. These disease correlations and the fact that HTLV-I and HTLV-II can be transmitted by transfusion have led to the recommendation that blood donors be screened for evidence of HTLV-I and HTLV-II infection. However, the connection between the virus and disease is not known. This project seeks to determine if current methods for screening blood donors are sufficient to detect both HTLV-I and HTLV-II infections. In addition, the purpose of this project is to examine molecular mechanisms which could explain the as yet poorly understood connection between HTLV and disease, thereby establishing a basis for HTLV-associated transfusion-transmitted disease. In the area of detection and blood safety, we coordinated a response to reports that HTLV-I tax sequences could be detected in up to 11% of normal healthy random blood donors who were negative on conventional HTLV-I/HTLV-II screening tests. This response was designed to determine the reproducibility of those reports. Laboratories from FDA, CDC, the Retrovirus Epidemiology Donor Study, and New York University analyzed specimens collected from 100 HTLV-I/II seronegative healthy random donors from the Baltimore, MD/Washington, DC area and from 11 individuals known to be infected with HTLV-I or HTLV-II. All test sites were blinded to the identity of each specimen, and methods of sample preparation and analysis by PCR were identical to those used by the laboratory at New York University which made the original observations. The results demonstrated that HTLV tax sequences could not be detected reproducibly in any of the HTLV-I/II seronegative healthy random donors, and indicated that current donor screening tests are effective at preventing the transfusion transmission of HTLV-I and HTLV-II. As a follow-up, similar studies are underway to screen a population of blood donors from the New York City area for the presence of tax sequences. These continuing studies are designed to address questions regarding the detection of tax sequences and blood donor demographics. We are also in the process of developing an assay to detect the presence of antibodies to HTLV tax. In the area of HTLV-I-associated neurological disease, we continued studies on the induction of TNF-alpha by purified HTLV-I Tax protein in NT2-N, post-mitotic cells that are remarkably similar to primary human neurons. In the past, we observed that transient exposure (as little as 5 minutes) of NT2-N to soluble Tax resulted in the synthesis of TNF-alpha, indicating that Tax need not be continually present. We have since demonstrated that TNF-alpha itself is sufficient to induce TNF-alpha synthesis, which will then sustain continued production of TNF-alpha.